U.S. patent application number 13/664275 was filed with the patent office on 2014-05-01 for ultrasonic communication system for communication through rf-impervious enclosures and abutted structures.
This patent application is currently assigned to The Board of Regents of the University of Oklahoma. The applicant listed for this patent is The Board of Regents of the University of Oklahoma. Invention is credited to John K. Antonio, Thomas D. Hosman, Mark B. Yeary.
Application Number | 20140119162 13/664275 |
Document ID | / |
Family ID | 50547078 |
Filed Date | 2014-05-01 |
United States Patent
Application |
20140119162 |
Kind Code |
A1 |
Yeary; Mark B. ; et
al. |
May 1, 2014 |
Ultrasonic Communication System for Communication Through
RF-Impervious Enclosures and Abutted Structures
Abstract
An ultrasonic communication system comprising an enclosure, a
first module and a second module is described. The enclosure has an
internal surface, an external surface, and defines at least one
metal channel. The first module comprises an ultrasonic transceiver
disposed within the enclosure. The first module is positioned on
the internal surface of the enclosure and is capable of
transmitting and/or receiving modulated ultrasonic waves via the
metal channel. The second module is positioned on the external
surface of the enclosure and is adapted to transmit and/or receive
modulated ultrasonic waves from the first module via the metal
channel.
Inventors: |
Yeary; Mark B.; (Purcell,
OK) ; Antonio; John K.; (Norman, OK) ; Hosman;
Thomas D.; (Edmond, OK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Board of Regents of the University of Oklahoma; The |
|
|
US |
|
|
Assignee: |
The Board of Regents of the
University of Oklahoma
Norman
OK
|
Family ID: |
50547078 |
Appl. No.: |
13/664275 |
Filed: |
October 30, 2012 |
Current U.S.
Class: |
367/178 |
Current CPC
Class: |
H04B 11/00 20130101;
G10K 11/24 20130101 |
Class at
Publication: |
367/178 |
International
Class: |
G10K 11/24 20060101
G10K011/24 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] This invention was made with government support under
SAFTEA-LU 1934 and SAFTEA-LU 1702 awarded by the Federal Highway
Administration. The government has certain rights in the invention.
Claims
1. An ultrasonic communication system, comprising: an enclosure
having an internal surface, an external surface, and defining at
least one metal channel; a first module comprising an ultrasonic
transceiver disposed within the enclosure, the first module
positioned on the internal surface of the enclosure and capable of
transmitting and/or receiving modulated ultrasonic waves via the
metal channel; and a second module positioned on the external
surface of the enclosure and adapted to transmit and/or receive
modulated ultrasonic waves from the first module via the metal
channel.
2. The ultrasonic communication system of claim 1 wherein the
enclosure is a shipping container.
3. The ultrasonic communication system of claim 1, further
comprising one or more sensors adapted to communicate data to the
first module, and wherein the first module is adapted to transmit
data from the one or more sensors to the second module via the
metal channel.
4. The ultrasonic communication system of claim 1, wherein the
enclosure is a pressurized enclosure.
5. The ultrasonic communication system of claim 4, wherein the
enclosure is a blowout preventer.
6. The ultrasonic communication system of claim 1, wherein the
modulated ultrasonic waves have a frequency of about 40 KHz.
7. The ultrasonic communication system of claim 1, wherein the
modulated ultrasonic waves have a frequency between 280 KHz and 330
KHz.
8. The ultrasonic communication system of claim 2, wherein the at
least one metal channel comprises a shipping container corner
post.
9. An ultrasonic communication system, comprising: a first
enclosure defining one or more first channels capable of
transmitting modulated ultrasonic waves; one or more first modules
comprising an ultrasonic transceiver positioned onto the first
channel; a second enclosure defining one or more second channels
capable of transmitting modulated ultrasonic waves; one or more
second modules comprising an ultrasonic transceiver positioned onto
the second channel; and wherein the first enclosure and the second
enclosure are positioned in an abutting interface connecting the
first channel and the second channel, and wherein the first module
and the second module communicate via the first and second
channels.
10. The ultrasonic communication system of claim 9, wherein the
first enclosure and the second enclosure comprise shipping
containers.
11. The ultrasonic communication system of claim 10, wherein the
shipping containers have one or more steel corner posts, and
wherein the first and second channels comprise one or more of the
steel corner posts.
12. The ultrasonic communication system of claim 9, wherein the
enclosure is a pressurized enclosure.
13. The ultrasonic communication system of claim 9, wherein the
modulated ultrasonic waves have a frequency of about 40 KHz.
14. The ultrasonic communication system of claim 9, wherein the
modulated ultrasonic waves have a frequency between 280 KHz and 330
KHz.
15. A method of forming an ultrasonic communication system
comprising the steps of: positioning a first module onto an
internal surface of an enclosure, the enclosure defining a metal
channel and being impermeable to radio frequency waves, the first
module capable of transmitting an ultrasonic modulated wave
externally of the enclosure via the metal channel; positioning a
second module externally of the enclosure, the second module
capable of receiving and/or transmitting modulated ultrasonic waves
from/to the first module; and actuating the first module and the
second module to communicate via the metal channel.
16. The method of claim 15, wherein the step of positioning the
first module includes the first module having a radiofrequency
transceiver.
17. The method of claim 15, wherein the step of positioning the
first module includes the first module having one or more magnets
for positioning the first module onto the internal surface of the
enclosure.
18. The method of claim 15, wherein the modulated ultrasonic waves
have a frequency of about 40 KHz.
19. The method of claim 15, wherein the modulated ultrasonic waves
have a frequency between 280 KHz and 330 KHz.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of the PCT Application
No. PCT/US11/34625, filed Apr. 29, 2011, which claims the benefit
of U.S. Provisional Application No. 61/329,932, filed Apr. 30,
2010, both of which are incorporated herein by reference in their
entirety.
BACKGROUND
[0003] Wireless radio frequency (RF) communication networks are
becoming ubiquitous. Furthermore, the number of devices being
connected to wireless networks is growing at a tremendous rate, as
the diversity of types of wireless devices being deployed is also
increasing. Devices having wireless RF interfaces range from tiny
sensors deployed in rain forests (e.g., to track environmental
conditions over time), to smart phones, to laptop computers, to
RFID tags for tracking products shipped around the world. As more
and more applications of wireless network technologies emerge, so
too do situations where wireless connections and networks are
needed, but for which wireless RF transmission is not possible. The
inventive concept describes a wireless ultrasonic communication
system that enables communication into and out of RF-impervious
enclosures and structures.
[0004] Applications of wireless networks that require connections
to devices that may reside inside RF-impervious enclosures,
including metal enclosures, are of increasing importance. One
example application where this occurs is in the tracking of
products and/or environmental conditions inside a sealed steel
shipping container. For reasons involving security and privacy, the
doors of shipping containers in transit cannot be opened.
Furthermore, holes or similar modifications may not be made to
these standardized shipping containers for reasons of structural
integrity and security, and protection of the items within the
sealed shipping container.
[0005] Much international shipping is carried in standardized
shipping containers, which can be transferred by ship, truck, or
rail. It is of great importance to both shippers and security
professionals to gather information about the contents, location,
and environmental conditions within such shipping containers.
Inspecting and tracking the contents of stacked shipping containers
in transit is problematic. In a shipyard, only the doors of some
shipping containers at the bottom of a stack may be accessed. In a
container ship, almost none of the shipping container doors are
accessible. Even when accessing the door of a shipping container is
possible, opening a shipping container door that is in transit may
violate international security policy and regulations.
[0006] The inside of shipping containers can be equipped with
electronic devices capable of storing and collecting a variety of
data. For example, an electronic file containing the contents of a
shipping container can be stored on a device within a shipping
container. Furthermore, environmental conditions such as
temperature and acceleration can be measured with sensors, and
stored electronically within a shipping container. Standard
wireless radio frequency (RF) communication technology cannot be
used to retrieve data from a closed shipping container because RF
transmissions cannot penetrate the metal surfaces of a shipping
container. RF signals are reflected by metal surfaces analogous to
the way light is reflected by mirrors. As a result, transmitting
digital information using RF networking technology is not possible
when attempting to transmit through and/or around stacks of
shipping containers. Boring holes in a shipping container for the
purpose of establishing direct wired connections to electronic data
inside a shipping container is not feasible because such interfaces
are not standard and would be difficult to maintain/operate if
there ever became such a standard. Furthermore, doing so would
generally compromise the structural integrity of the shipping
container and alter the standardized structure. The inability to
read electronic information stored inside the shipping container
(e.g., RFIDs, sensor readings, electronically stored manifests)
severely limits the efficiency and effectiveness of security
professionals and inspectors in performing their duties. It also
limits the ability of commercial shipping companies in tracking and
monitoring the status of packages inside shipping containers in
transit, as well as monitoring the environmental conditions inside
a shipping container.
[0007] Some shipping containers are not entirely constructed of
metal. For example, a floor of shipping container is provided with
metal joists, but may have a plywood bottom. Even though RF
transmissions may pass through plywood material, significant
problems exist when trying to communicate to the interior of the
shipping container using RF transmissions. This is because the
bottom of the shipping container is typically shielded by a top
metallic surface of an adjacent shipping container upon which it is
stacked, or a ground plane (such as the Earth, or a metallic floor
of a ship) upon which the shipping container is positioned.
[0008] Shipping containers are typically twenty or forty feet long,
eight feet wide, and eight and one-half feet tall. They are
constructed with four structural steel corner posts terminated at
the top and the bottom in cast steel corner blocks. Shipping
containers can be stacked up to twelve high, resulting in a
towering structure the height of a ten story building. Expansive
grids of stacked shipping containers are commonly found in
shipyards and deep within the hulls of huge container ships.
Shipping containers are positioned and stacked with massive,
precision cranes. To make efficient use of limited space, adjacent
stacks of shipping containers are typically positioned very close
together in shipyards. On container ships, adjacent stacks of
shipping containers are often placed in contact with one another
and/or held in place with locking pins and/or bracing straps to
provide stability. When stacked, the weight of the shipping
containers and their cargo is carried by the continuous columns of
corner posts at each corner of the stack. For structural and
security reasons, the doors of a shipping container must not be
opened in transit, and holes may not be drilled through a shipping
container's walls.
[0009] Closed shipping containers act as Faraday cages, which
preclude the use of traditional radio frequency (RF) communication
schemes for transmitting data through these metal structures.
Traditional radio frequency communication schemes are not capable
of transmitting signals through metal enclosures. Ultrasound
presents a promising alternative. Steel is an excellent conduit of
ultrasonic energy, and ultrasound transmission requires no
compromise of the shipping container's structural or security
integrity.
[0010] Previous researchers have investigated ultrasonic
communication in other applications. A patent application [1]
exists, for example, for an application involving sensor
communication within an airframe; sensor communication along the
surface of a single shipping container is also mentioned. However,
this prior research: (i) does not consider communication from
within a shipping container to outside a shipping container; (ii)
does not consider communication among stacked shipping containers;
(iii) does not consider two way communication; and (iv) did not
proceed to the system prototyping stage.
[0011] Research was done at Oak Ridge National Laboratories in 1993
and further in 1999 regarding ultrasonic communications [2]. These
researchers successfully built a demonstration system to
communicate using ultrasound in air, and also carried out
experiments in various types of pipes that might be found in a
typical building water supply. The demonstration system built as
part of this project consisted of three work boxes and a laptop
running LabView Virtual Instruments at each end of the
communication channel.
[0012] Other research on underwater communication with autonomous
underwater vehicles (AUVs) was conducted at Florida Atlantic
University in 1996 [3]. Their research involved using multi-tone
frequency shift keying (MFSK) and differential phase shift keying
(DPSK) to communicate in shallow water.
[0013] The most mature applications involving ultrasonics do not
involve ultrasonic communications, but instead originate from the
fields of non-destructive testing and medical imaging. In
nondestructive testing, the propagation of high frequency (several
MHz) ultrasound is transmitted through various materials for the
detection of material discontinuities such as flaws or cracks [4].
In medical applications, ultrasonic reflections are the basis of
forming images. Although there is an extensive body of data related
to these types of applications, the high-frequency (and
high-resolution) transducers designed to operate in these regimes
are costly, and therefore may be impractical for the types of
application domains where ultrasonic communications would be
employed.
[0014] Another application involving the problem of transmitting
information through an RF-impervious enclosure arises in oil and
gas applications, including downhole drilling and extraction. For
reasons involving human and environmental safety and protection,
and prevention of damage to various components of the drilling rig,
it is important to monitor pressure, and possibly other parameters,
such as temperature, using sensors located inside highly
pressurized vessels and enclosures, including blowout preventers
(BOPs). These highly pressurized enclosures are enormous in size,
typically constructed with extremely thick, strong steel
components. Due to the extreme conditions and pressures present
inside these enclosures, it is not possible or practical to
consider boring holes through the walls of these structures with
the purpose of passing wiring for making connections between the
inside and outside of the enclosure.
[0015] In the field of oil and gas exploration and extraction, for
reasons of human and environmental safety and prevention of damage
to components of the rig, it is increasingly desirable to be able
to monitor pressure and/or other sensor readings taken from within
the enclosure associated with a blowout preventer (BOP) or a BOP
stack. The goal is to transmit pressure measurement readings taken
inside a BOP enclosure (or other associated enclosure and/or pipe)
to outside the BOP without compromising the structural integrity of
the BOP itself (e.g., without boring holes in the thick steel walls
of the structure). Pressures can be upwards of 20,000 pounds per
square inch (psi), thus failures of the mechanical structure of the
BOP can be catastrophic and must be prevented. Transmitting
electronic measurements taken from the inside of a pressurized
component, such as a BOP, to the outside, is not possible with RF,
because RF does not transmit through steel. Also, it is not
possible to use a "wired connection" to transmit the readings of a
sensor on the inside of the BOP to the outside, because it is not
allowed to bore a hole through a wall of the BOP; doing so would
compromise its structural integrity and ability of the BOP to
withhold extremely high pressures.
[0016] The valve(s) of a BOP are closed, either manually or
automatically, in order to prevent extremely high-pressure well
fluids from blowing out of the well rig, which could otherwise harm
the well operators and/or compromise or destroy the rig itself.
Thus, it is important to accurately monitor the pressure the BOP is
withstanding. One type of BOP, called an annular type, stops the
flow of fluids out of the annulus, which is the area between the
outside of the drill pipe and the casing of the wellbore. By
pumping dense mud into the wellbore, down the drill string,
downhole pressure can be overcome. Having accurate measurements of
pressures within the BOP would enable operators to know the density
of mud that should be used to kill the well and/or know at what
point the pressures are safe for possible continued operation or
drilling. Having accurate measurements of pressures is also
important during testing and maintenance phases of the BOP
lifecycle. The requirement of measuring extremely high pressures
remains; whether they occur in operation in the field, or in a
controlled testing environment. The inventive concept described
enables ultrasonic communication mechanisms to transmit pressure
readings (and/or other sensor readings) from an ultrasonic
communication module mounted on the inside of the BOP, through its
thick steel wall, to a receiving module mounted on the outside of
the BOP. Once the sensor measurement reading is available on the
outside of the BOP, it can be transmitted from the externally
mounted module to the desired final destination using traditional
(e.g., wired or RF) or ultrasonic communication channels, as
appropriate.
[0017] In addition to measuring pressures from within a single BOP,
the inventive concept also addresses the requirement of
communicating pressure readings among BOPs forming a BOP stack. A
BOP stack is a structure of two or more BOPs used to control
pressure in a well. A typical stack may have different types of
BOPs, e.g., annular types at the top and ram types near the bottom
of the stack. Communication of pressure readings among a stack of
BOPs provides the ability to implement automatic control mechanisms
in which pressure readings from all BOPs can be considered in
making timely control and actuation decisions. Additionally,
ultrasonic communication modules residing on multiple BOPs of a
stack can form a relay network for communicating information
measured at one location of the stack to another location on the
stack, which may serve as a communication gateway for communicating
to other components of the rig or locations where operators of the
rig can monitor pressure readings and take necessary action.
[0018] Accordingly, a need exists in the prior art to obtain
information from inside sealed RF-impermeable enclosures, without
compromising the enclosure's integrity. To such systems and methods
for transmitting information through RF-impermeable sealed
enclosures the inventive concept disclosed herein is directed.
SUMMARY
[0019] In one aspect the inventive concept disclosed herein is
directed to an ultrasonic communication system. The ultrasonic
communication system is provided with an enclosure, a first module
and a second module. The enclosure has an internal surface, an
external surface, and defines at least one metal channel. The first
module comprises an ultrasonic transceiver disposed within the
enclosure. The first module is positioned on the internal surface
of the enclosure and is capable of transmitting and/or receiving
modulated ultrasonic waves via the metal channel. The second module
is positioned on the external surface of the enclosure and is
adapted to transmit and/or receive modulated ultrasonic waves from
the first module via the metal channel.
[0020] In another aspect, the inventive concept disclosed herein is
directed to an ultrasonic communication system, comprising a first
enclosure defining one or more first channels capable of
transmitting modulated ultrasonic waves and one or more first
modules comprising an ultrasonic transceiver positioned onto the
first channel. A second enclosure defines one or more second
channels capable of transmitting modulated ultrasonic waves and has
one or more second modules comprising an ultrasonic transceiver
positioned onto the second channel. The first enclosure and the
second enclosure are positioned in an abutting interface connecting
the first channel and the second channel such that the first module
and the second module communicate via the first and second
channels.
[0021] In yet another aspect, the inventive concept disclosed
herein is directed to a method of forming an ultrasonic
communication system comprising the steps of: (a) positioning a
first module onto an internal surface of an enclosure, the
enclosure being impermeable to radio frequency waves, the first
module capable of transmitting an ultrasonic modulated wave to an
external surface of the enclosure; (b) positioning a second module
onto an external surface of the enclosure, the second module
capable of receiving and/or transmitting modulated ultrasonic waves
from/to the first module.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0022] Like reference numerals in the figures represent and refer
to the same or similar element or function. Implementations of the
disclosure may be better understood when consideration is given to
the following detailed description thereof. Such description makes
reference to the annexed pictorial illustrations, schematics,
graphs, drawings, and appendices. In the drawings:
[0023] FIG. 1 shows an exemplary embodiment of ultrasonic
transducers according to the instant disclosure.
[0024] FIG. 2 is a graph showing transmission efficiency versus
frequency for a pair of transducers according to the instant
disclosure.
[0025] FIG. 3 is a graph showing received signal voltage versus the
pressure with which the transducer is placed in contact with the
opposing surface with the transmitted signal at 296 KHz and 6 volts
peak-to-peak according to the instant disclosure.
[0026] FIG. 4 is an embodiment of a corner post setup showing two
corner posts held in compression with hand hoist and nylon
strapping according to the instant disclosure.
[0027] FIG. 5 is a graph of measured (received) voltages as a
function of distance between transmission and receiving transducers
along the length of a corner post according to the instant
disclosure.
[0028] FIG. 6 is an embodiment of a corner block interface of two
abutting corner posts according to the instant disclosure.
[0029] FIG. 7 is a block diagram illustrating an exemplary MFSK
encoding scheme according to the instant disclosure.
[0030] FIG. 8 is a logical block diagram of an exemplary ultrasonic
communication system constructed in accordance with the presently
disclosed inventive concept(s).
[0031] FIG. 9 is a graph of the following signals from top to
bottom: LM567 output trigger; transmitted MFSK signal; received
signal; and amplified signal according to the instant disclosure.
The first signal (on the left) is a sync tone; the second smaller
signal is a MFSK waveform.
[0032] FIG. 10A is a timing diagram which depicts transmission of
the sync tone (e.g., sine wave) and the data signal (shown in the
middle), according to the instant disclosure.
[0033] FIG. 10B is a timing diagram which depicts detection and the
sampling of the data according to the instant disclosure.
[0034] FIG. 11 is a graph of FFT of received hexadecimal symbol
0xAAAA by a communication system according to the instant
disclosure.
[0035] FIG. 12 is a graph of FFT of received hexadecimal symbol
0x5555 by a communication system according to the instant
disclosure.
[0036] FIG. 13 is a block diagram of an exemplary module adapted to
be positioned on an interior surface of an enclosure according to
the instant disclosure.
[0037] FIG. 14 is a block diagram of an exemplary embodiment of a
module adapted to be positioned on an exterior surface of an
enclosure.
[0038] FIG. 15 is a diagrammatic view of an exemplary embodiment of
two modules according to the instant disclosure.
[0039] FIG. 16 is a diagrammatic view of another exemplary
embodiment of two modules according to the instant disclosure.
[0040] FIG. 17A is a perspective view of an enclosure formed by a
shipping container.
[0041] FIG. 17B is a cross-sectional view of the enclosure depicted
in FIG. 17A.
[0042] FIG. 18A is a front-elevation view of an exemplary stack of
shipping containers according to the instant disclosure.
[0043] FIG. 18B is a front-elevation view of an exemplary
embodiment of a compression interface formed by two abutting
shipping container corner blocks within the stack of shipping
containers depicted in FIG. 18A.
[0044] FIG. 19 is a diagrammatic view of an example of two stacked
shipping containers according to the instant disclosure.
[0045] FIG. 20 is a diagrammatic view of an embodiment of a
shipping container stack according to the instant disclosure.
[0046] FIG. 21 is a diagrammatic view of three stacked shipping
containers showing a communication system according to the instant
disclosure.
[0047] FIG. 22 is a diagrammatic view of three stacked shipping
containers showing a communication system according to the instant
disclosure.
[0048] FIG. 23 is another diagrammatic view of an embodiment
showing a stack of N shipping containers according to the instant
disclosure.
[0049] FIG. 24 is a diagrammatic view showing M and L stacks of N
shipping containers according to the instant disclosure.
[0050] FIG. 25 is a diagram of a sampling plan in the frequency
domain according to the instant disclosure.
[0051] FIG. 26 is a block diagram of an exemplary module according
to the instant disclosure.
DETAILED DESCRIPTION
[0052] Before explaining at least one embodiment of the inventive
concept disclosed herein in detail, it is to be understood that the
inventive concept is not limited in its application to the details
of construction and the arrangement of the components or steps or
methodologies set forth in the following description or illustrated
in the drawings. The inventive concept disclosed herein is capable
of other embodiments or of being practiced or carried out in
various ways. Also, it is to be understood that the phraseology and
terminology employed herein is for the purpose of description and
should not be regarded as limiting in any way.
[0053] In the following detailed description of embodiments of the
disclosure, numerous specific details are set forth in order to
provide a more thorough understanding of the inventive concept.
However, it will be apparent to one of ordinary skill in the art
that the inventive concept within the disclosure may be practiced
without these specific details. In other instances, well-known
features have not been described in detail to avoid unnecessarily
complicating the instant disclosure.
[0054] A conformal ultrasonic communication system based on
multi-tone FSK (MFSK) has been developed and evaluated using steel
corner posts from shipping containers as the communication medium.
The ultrasonic communication system is configurable, consisting of
two or more modules with one of the modules being an inside module
and the other being an outside module. However, as discussed in
more detail below, it should be understood that the inside and
outside modules do not have to be located on the same container or
enclosure, or even on the same stack of shipping containers or
enclosures so long as at least one inside module can communicate
with at least one outside module.
[0055] As used herein, the term "metal channel" or simply "channel"
shall be understood to mean a metal of an enclosure, including the
structural corner posts for the shipping container application,
which is used as the ultrasonic communication medium.
[0056] The term "module" will be used when referring to the
operation of the inside module and the outside module. The modules
are mounted to metal surface(s) forming a metal channel and
preferably utilize ultrasonic transducers to send and receive
modulated signals through the metal channel. The modules may also
make use of a controller having an inexpensive digital signal
processor (DSP) chip for modulating and demodulating MFSK signals.
For the shipping container application, experiments were conducted
that achieve data rates of approximately 800 bytes-per-second
(bps). Experiments related to two scenarios for the shipping
container application were investigated: (1) communicating through
one shipping container and (2) communication between stacked
shipping containers. For the second case, experiments were
conducted with modules on two separate corner posts that are under
compressive load. This demonstrates the ability to establish
ultrasonic communication among arrays of shipping containers that
are abutted with patterns of contact.
[0057] The presently disclosed and claimed inventive concept(s)
focus on the development and logistical implications of an
ultrasonic communication system that may employ the coupled metal
components of stacked shipping containers or pressurized enclosures
as ultrasound communication conduits. More particularly, the
inventive concept disclosed herein describes an ultrasonic
communication solution in which the structure of the enclosure
itself serves as the communication channel for ultrasonic
signaling. This approach enables a wireless connection to be made
between the inside and outside of a sealed, RF-impervious
enclosure. The most basic architecture of the ultrasonic
communication system includes at least two ultrasonic-based
communication modules, one mounted to a surface inside the
enclosure and the other mounted on the outside surface of the
enclosure. Sensors and sensor readings and/or other stored
electronic information may be co-located with a module mounted on
the inside of the enclosure. Alternatively, sensors and sensor
readings and/or other stored electronic information may be stored
at different locations inside the enclosure and be transmitted to
the module mounted inside the enclosure using any number of
communication schemes and mediums. In the described inventive
concept, data present on the module mounted inside the enclosure is
encoded, modulated, and transmitted using ultrasonic signaling into
the enclosure structure using an ultrasonic transducer held in
contact with the inside surface of the enclosure. A module in
contact with a surface on the outside of the enclosure receives the
transmitted ultrasonic signals, which are then demodulated and
decoded to reconstruct the originally transmitted information.
[0058] Another, more advanced ultrasonic communication architecture
involves mounting ultrasonic communication modules on two or more
RF-impervious enclosures, or structures, which are abutted to one
another. In this architecture, two or more modules can participate
in a relay network by using the aggregate structure(s) formed by
the abutment of the enclosures, or structures, as ultrasonic
communication channel(s). Example scenarios where the utility of
this type of architecture arises include stacks of shipping
containers and BOP stacks.
[0059] The conformal modules of this communication system establish
two-way communication and are capable of participating in a relay
network within a stack of shipping containers or pressurized
enclosures or even a collection of stacks of shipping containers or
pressurized enclosures in which one or more shipping containers in
adjacent stacks are either directly in contact or indirectly in
contact through accessory metal structures such as bracings.
[0060] The presently disclosed and claimed inventive concept(s)
utilizes the coupled metal structures of stacked shipping
containers or pressurized enclosures as ultrasound communication
conduits through which data is communicated through modulated
ultrasonic signals. A stack of shipping containers or pressurized
enclosures forms a communication network in which shipping
containers or pressurized enclosures on the stack contain
communication modules (ultrasonic receiver/transmitter pairs) used
to initiate, relay, and/or respond to communications signals
to/from abutted shipping containers or BOPs, or shipping containers
or pressurized enclosures that are connected indirectly.
[0061] In one version, the presently disclosed and claimed
inventive concept(s) describes an ultrasonic communication system
that employs the coupled metal components of stacked shipping
containers as ultrasound communication conduits. To read the
contents of data inside one or more shipping containers in a stack,
an operator need only make contact with one external shipping
container surface in the stack using an ultrasonic coupler. Once
contact is made, the contents of the shipping containers can be
queried by the operator. Also, the operator can send control
signals to selected shipping containers (e.g., to adjust
environmental control settings such as temperature and humidity). A
stack of shipping containers effectively forms a communication
network, enabling the operator access/control data of all shipping
containers in the stack via one external access point on one
shipping container.
[0062] The presently disclosed and claimed inventive concept(s) can
revolutionize the tracking, security, and quality control of
shipping container's contents. Allowing shipping containers to be
opened and examined while in transit is not possible in practice
due to general inaccessibility of shipping container doors. Also,
allowing a shipping container to be opened during international
transit allows for security breeches and violations of shipper's
and/or receiver's confidentiality. The presently disclosed and
claimed inventive concept(s) allows a shipping container's contents
to be checked systematically and arbitrarily without the need to
open any shipping container doors, with enhanced security and
integrity of the shipped container.
[0063] The following five exemplary modes of ultrasonic
communication capability are contemplated, but these do not limit
the scope of the inventive concepts regarding other modes:
[0064] One Enclosure Unidirectional Communication (OEUC)--involves
one ultrasonic transmitter placed inside a shipping container or a
pressurized enclosure and one ultrasonic receiver placed on the
outside of the shipping container or pressurized enclosure.
[0065] One Enclosure, Duplex Communication (OEDC)--includes
co-located transmission and receiving capabilities, both inside and
outside a shipping container or a pressurized enclosure. Using
OEDC, it is contemplated that an operator on the outside of the
shipping container or pressurized enclosure can first query, then
receive, data from inside the shipping container or pressurized
enclosure. Also, the duplex communication feature enables re-send
protocols to be designed and developed to be used to combat channel
noise and multipath effects.
[0066] Stacked Enclosures, Unidirectional Communication
(SEUC)--communication between stacked shipping containers or
pressurized enclosures. Two stacked shipping containers can be
emulated using two corner posts--each terminated with a corner
block--that are coupled by compressive loading (see FIG. 4). The
objective contemplated by this scenario is that an ultrasonic
transmission can be made to: traverse from a transmitter attached
to the first corner post; pass through the mechanically coupled
corner blocks; and be received successfully by a receiver located
on the second corner post.
[0067] Stacked Enclosures, Duplex Communication (SEDC)--duplex
communication between stacked shipping containers or pressurized
enclosures. This mode of operation enables a stack of shipping
containers or pressurized enclosures to be modeled as a linear
network graph in which a given pair of nodes in the graph can
communicate by employing intermediate nodes as relays/vias. This
mode will also enable broadcast- and accumulation-type
communication patterns to be implemented.
[0068] General Array of Enclosures (GAE) an arrangement of stacks
of shipping containers or pressurized enclosures in which adjacent
stacks may be aligned in a horizontal (side-by side) and/or depth
(back-to-front) manner. This arrangement generalizes the linear
array model associated with a single stack to either a
two-dimensional grid or a three-dimensional cube. This arrangement
of shipping containers or pressurized enclosures provides a
communication network topology that may be represented by a
two-dimensional grid or three-dimensional cube (see FIG. 24). Even
if some shipping container(s) or pressurized enclosures on some
stacks are not in sufficient mechanical contact with their
counterpart shipping container(s) or pressurized enclosures on
another adjacent stack, it is still possible for communication to
be established by utilizing mechanically-connected routes that
exist between a shipping container or pressurized enclosure
desiring communication with another shipping container or
pressurized enclosure.
[0069] Features of preferred embodiments of an ultrasonic
communication system according to the instant disclosure may
include but are not limited to:
[0070] Modules are sleeping (low power consumption) when not
participating in communication;
[0071] Modules support various modes of communication including
ultrasound, RF, IR, and wired connections;
[0072] Modules can be constructed with RF pervious material(s) to
protect antenna (e.g., thick rugged plastic);
[0073] Transmitting module sends pilot tone--receiving module may
detect pilot tone using low power tone detector circuitry such as
the LM 567 Tone Decoder. The detection circuitry may also be
passive or be active and consume a small amount of energy. In one
embodiment, the detection circuitry can include a very high Q LC
(inductor capacitor) circuit tuned to the frequency of the pilot
tone to detect (pass) a received tone from the transducer (which is
passive). In this example, it is believed that there should be
enough electrical energy conversion due to the piezoelectric
conversion to drive the LC circuit and wake up the rest of the
circuit. In another embodiment, the detection circuitry can include
a low power tone detector chip, which is not "passive" but is
nearly passive (because it consumes very little energy while it
listens for the tone). An exemplary passive circuit may include a
passive resonant LC circuit connected directly to the transducer.
The output of this circuit would then be compared to ground using a
comparator, and the output of the comparator represents
detection.
[0074] Pilot tone detection used as trigger to power-up
communication circuitry of receiving module;
[0075] Pilot tone detection timing used to synchronize
communication between transmitting and receiving modules;
[0076] Ultrasonic communication may use two or more distinct
frequency bands: one for control/synchronization and another for
encoded data;
[0077] Undersampling used by receiving module to reduce sampling
rate of A/D converter--where undersampling is defined as
intentional sampling at a lower rate to fold (or alias) specific
tones to desired low frequency locations in the spectrum. In
practice, undersampling can effectively reduce the required
sampling rate of the A/D converter by an order of magnitude.
[0078] Undersampling reduces power consumption and cost of
receiving module since power consumption is proportional to
sampling rate;
[0079] Coherency among sampling rate, DFT size, and selected
frequency tones is performed to maximize detection of modulated
data transmission.
[0080] The following is a description of an example of the
ultrasonic communication system for causing communication between a
module installed on an interior surface of a metal channel formed
by a shipping container and another module installed on an exterior
surface of the metal channel formed by either the same or different
shipping container. However, it should be understood that the
ultrasonic communication system can be used for establishing
communication among numerous shipping containers or pressurized
enclosures that are abutted in arbitrary ways and for various other
purposes as discussed above.
[0081] In an exemplary embodiment, at least one module is mounted
inside a shipping container and at least one other module is
mounted on the outside of either the same shipping container or
another shipping container that is directly or indirectly in
contact with the first. However, it is possible that some useful
scenarios may involve only communication among modules mounted on
the insides of distinct shipping containers.
[0082] Modules mounted on the inside of a shipping container might
go several months without the opportunity to charge/replace
batteries, and thus are more power constrained than modules used by
an operator as described above. For this reason, the modules'
circuitry can be designed to be power-aware; remaining in a
low-power "sleep" mode when not actively participating in
communication with other modules. Modules mounted inside a shipping
container that are in transit onboard a ship may employ energy
harvesting techniques that convert motion and/or vibrations to
electrical energy used to charge the power supply. Alternatively,
mechanisms for the conversion of thermal/heat energy to electrical
energy may also be employed to charge power supplies of modules
mounted inside shipping containers for extended periods of time.
Modules allow attachment of various environmental sensors and have
facilities for storing data gathered from these sensors. In
addition to the ultrasonic mode of communication, they may also
have other modes of communication including RF, IR, and wired
connections. Modules have the ability to gather and store
information from sensors that are co-located on the module and from
information collected through communication with other modules.
Operators that use modules as described above can store data for
later upload to a database through interfaces with wired or
wireless local area networks and/or the internet.
[0083] An exemplary embodiment of ultrasonic transducers 100a-b is
shown in FIG. 1, and may include piezoelectric materials.
Alternatively, an electro-mechanical "tapping" device could be used
for much lower frequencies than ultrasound (in the range of tens or
100 s of Hertz), for example. Piezoelectric materials expand and
contract with applied voltages. Conversely, they produce a voltage
in response to deformation. The electrical characteristics of a
piezoelectric element resemble those of a capacitor. Piezoelectric
elements are fast and precise in the realm of mechanical motion and
motion detection. Because of the two way nature of the effect,
piezoelectric elements can be used as both ultrasonic transmitters
and receivers. A given transducer 100a-b may have one or more
resonant frequencies depending on its design and construction.
Ultrasound energy is much more efficiently transmitted and received
by the transducer 100 at these frequencies. A transducer 100 may be
used as described in this study [5].
[0084] By pulsing one transducer 100a--with a receiving transducer
100b clamped face-to-face--characterization of the transmission
efficiency of a transducer pair 100a-b can be determined over a
wide frequency spectrum. Data gathered in this way can be used to
produce an empirical frequency response curve 102, an example of
which is shown in FIG. 2. From FIG. 2, it is clear that the
employed transducers 100a-b exhibit two major regions of resonance.
The first occurs around the manufacturer specified resonant
frequency of the transducers 100a-b, at about 40 KHz [5]. It is to
be understood that the term "about" as used herein should be
interpreted to include a 15-20% variation due to environmental,
manufacturing, or other factors/issues. The second occurs on a band
beginning near 280 KHz and extending to approximately 330 KHz
(although other frequency bands could be used). This second band is
well displaced from the nominal 40 KHz center frequency of the
transducers 100a-b and produces a better voltage response by a wide
margin. In addition to the effect that transmission frequency has
on transmission efficiency, the overall transmission efficiency is
also dependent upon the pressure with which a transducer 100a-b is
mounted to the opposing surface.
[0085] As illustrated by FIG. 3, transmission efficiency is
primarily an increasing function of the value of pressure applied
in mounting the transducer 100a-b to the surface. From FIG. 3,
observe that there is a reasonable range of pressures within which
the transmission efficiency is relatively constant.
[0086] Shown in FIG. 4 is an experimental setup 106 of first and
second corner posts 104a-b of shipping containers were acquired for
demonstrating a communication system according to the instant
disclosure. The first and second corner posts 104a-b are laying
horizontally on a support structure 108, and are held in
compression against one another.
[0087] FIG. 5 is an example of measurements taken using the
experimental setup 106, which illustrates how received signal
strength degrades as a function of distance between transmitting
transducer 100a and receiving transducer 100b. Importantly for
shipping container applications, it was discovered that ultrasonic
signals can be transmitted from the first corner post 104a, and
received on the second corner post 104b abutted to the first corner
post 104a.
[0088] FIG. 6 shows a first corner post 104a had a first corner
block 110a and the second corner post 104b has a second corner
block 110b. Also shown is an exemplary embodiment of an abutting
interface 111 of the first and second corner blocks 110a-b at the
end of the first and second corner posts 104a-b.
[0089] Referring now to FIG. 7, Multi-Tone Frequency Shift-Keying
(MFSK), which is a generalization of frequency-shift-keying (FSK),
is known to be well-suited for fading channels [6]. Ultrasonic
signals transmitted through mediums such as steel or water are
subjected to extreme fading effects. In the case of transmitting
ultrasound through a steel beam, fading is primarily due to two
phenomena: (1) multipath effects due to multiple reflections off of
channel boundaries and (2) the effect of multiple Lamb waves
traveling through the channel at different velocities [1].
[0090] For example, let N denote the set of tones available for
defining symbols. Traditional FSK represents different symbols with
individual sinusoidal tones. Thus, for a pool of N tones, FSK can
encode at most N symbols. MFSK uses different combinations of
multiple frequencies (summed tones) to encode symbols [6]. The MFSK
scheme in which exactly Q tones are used at a time is known as
Q-tone FSK, which can encode symbols. On the transmission side, an
M-bit data word 112 may be input to a symbol encoder module 114,
which produces an N-bit symbol 116 as shown in FIG. 7. For Q-tone
FSK, exactly Q of these N bits are unity, which correspond to
selected tones of the symbol.
[0091] In principle, an MFSK receiver 118 of a module 140 (FIGS.
13-14) may employ a bank of matched filters with center frequencies
tuned to each of the N tones. In an exemplary implementation of the
inventive concept(s) disclosed herein, the received signal can be
digitized, and a fast Fourier Transform (FFT) can be performed on a
receiver's data signal processor (DSP) 122. It is to be understood,
however, that digital or analog matched filters tuned to the N
tones can be used with the inventive concept(s) disclosed herein as
well. The receiver 118 thresholds the magnitude of the values from
the FFT frequency bins associated with the N tones. If exactly Q
tones exceed prescribed thresholds, then the corresponding symbol
was detected. Otherwise, the receiver 118 declares a transmission
error.
[0092] In one embodiment of a communication system 120 according to
the instant disclosure, N=16 tones may be used. In such embodiment,
a select group of frequencies within a specific band may be
considered. The carrier frequencies may be in the band of 280 to
320 KHz, for example. These carrier frequencies, fk are listed in
Table I. Note that the spacing of the tones is not uniform across
this range. These selected frequencies have been determined
experimentally by maximizing the frequency response through the
channel. Further optimization in selecting frequencies could
include the impact of choosing frequencies so that the employed
undersampling rate (described in the following paragraph) results
in coherency for the FFT size used.
TABLE-US-00001 TABLE I Tone Number Frequency Value (KHz) f0 284.0
f1 286.5 f2 287.5 f3 290.0 f4 292.0 f5 294.0 f6 296.0 f7 297.5 f8
299.9 f9 302.3 f10 303.6 f11 304.3 f12 305.8 f13 308.2 f14 314.0
f15 316.2
[0093] A practical key to successfully realizing the FFT approach
at the receiver 118 may be the design of an implementation of an
efficient digital sampling procedure based on the principle of
undersampling. This approach may enable the sampling of the
received signal to be at a rate of only 165 KHz, which is just
slightly over one-half the maximum tone frequency of 316.2 KHz. Had
this undersampling procedure not been utilized, then an ADC
sampling rate of around 3 MHz would have been required. Sampling at
such a high rate is impractical for the envisioned applications
that have severe cost and power constraints. By definition,
"bandpass sampling" is a special form of undersampling that
translates a high frequency bandpass signal to a baseband frequency
[7]-[10]. Moreover, bandpass sampling is a "software defined radio"
concept that provides a technique of reduced sampling speeds, which
directly translates to reduced power consumption (as the authors
have been able to demonstrate on other projects, i.e. [11]).
[0094] Coherence in a sampled waveform is advantageous in order to
use data analysis techniques, such as the discrete Fourier
transform (DFT). It is assumed that this DFT may be implemented in
its pure form or as a fast Fourier transform (FFT). In general,
coherency as used herein will allow for an integer number of
samples.
[0095] Let:
[0096] Number of tones: N
[0097] Length of the discrete Fourier transform: L=2m, where m is
an integer
[0098] Sampling frequency: Fs
[0099] Tone number: f0, f1, . . . , fN-1
[0100] Integer number of periods or cycles in length L: P
[0101] The discrete Fourier transform for a sequence of length L is
defined here as:
X [ k ] = n = 0 L - 1 x [ n ] - j 2 .pi. N nk ##EQU00001##
[0102] where the variable "k" denotes a particular frequency bin.
The discrete frequency related to each k is an integer multiple of
Fs/L, and k ranges from 0 to L-1.
[0103] Each analog tone {f0, f1, . . . , fN-1} must be selected so
that it can be uniquely resolved by one frequency bin of the
discrete Fourier transform. In particular, each selected tone is a
multiple of the discrete frequency resolution: [Fs/2]/[L/2].
[0104] In order to ensure coherency, an integer number of periodic
cycles of the sampled waveform must be collected and processed by
the discrete Fourier transform. This will be ensured when:
F S f n = P 2 m , ##EQU00002##
n=0, 1, . . . , N-1
[0105] where, fn, corresponds to each tone {f0, f1, . . . ,
fN-1}.
[0106] FIG. 8 shows a logical block diagram of an exemplary
embodiment of a communication system 120 according to the instant
disclosure. A sync tone 124 is sent at the beginning of a
transmission cycle, which corresponds to the modulation clock 126
rising to its high state. When the modulation clock 126 falls to
its low value at half the clock period, the MFSK symbol 116 is
transmitted. Note that while FIG. 8 shows the transmitting
transducer 100a and the receiving transducer 100b in contact with
different physical sides of metal channel 128, the transmitting
transducer 100a and the receiving transducer 100b may or may not be
on the same physical side of the metal channel 128. Furthermore,
the metal channel 128 may physically involve one or more abutted
corner posts 104a-b (not shown) with transducers 100a-b mounted on
one or both physical sides of the metal channel 128.
[0107] Initial focus was on designing and constructing a receiver
118 to receive and decode MFSK symbols 116 from a metal channel 128
(which may be a corner post 104a-b). On the transmission side, an
arbitrary signal generator 129 (Tektronix 81150A), and an amplifier
circuit 131 were used to produce and transmit the MFSK symbols 116
(In a more complete production implementation, the MFSK signal may
be generated on the DSP 122). An exemplary embodiment of a receiver
118 may include an amplifying and biasing circuit 133, an LM567
tone decoder 135, and a DSP 122. The amplifying and biasing circuit
133 may be used to amplify the received signal in order to utilize
the full dynamic range of the DSP 122 on-board analog-to-digital
converter (ADC) 121. The circuit had a SNR of 27 dB and a gain of
600 v/v. This amplifies the signal from 5 mVpp to 3 Vpp on a 1.5 V
bias.
[0108] The LM567 tone decoder 135 implementation was chosen because
it provides an easy and inexpensive way to detect the
synchronization tone. Instead of the DSP 122 constantly sampling
and performing filtering to detect synchronization, the DSP 122 can
be put into a low power wait state until the sync tone is detected
by the LM567 tone decoder 135. This is a key in keeping the
communication module 140 as energy efficient as possible (in
addition to providing synchronization necessary to time when the
receiver 103b begins sampling the received modulated data
signal).
[0109] Using the DSP 122 is desirable because it is able to rapidly
compute the spectrum of the received signal via the FFT. The Texas
Instruments TMS320LF2407A DSP 122 was chosen for this project,
based on its low-cost aspects, features, and low-power consumption.
The F2407A is a 16-bit fixed point DSP 122 capable of operating at
speeds up to 40 million instructions per second. (Other
implementations may explore the use of other DSP 122 chips
including ones like the SHARC Processor from the Analog Devices
Company). Other implementations may include the use of application
specific integrated circuits (ASICs), field programmable gate
arrays (FPGAs), or other digital logic implementations. Completely
analog circuit implementations could also be deployed.
[0110] The DSP 122 has an internal flash memory (32K, not shown),
which allows for rapid prototyping and eliminated costly off-chip
memory. This particular DSP 122 also has an on board ADC 121 with a
500 ns conversion time. This feature mitigated the need of an
additional off board converter.
[0111] FIG. 9 shows actual scope traces of the transmission of the
sync tone followed by the MFSK signal. As the MFSK signal travels
down the metal channel 128, the signal degrades and fades but is
eventually picked up by the receiving transducer 100b. This signal
was next amplified to 3Vpp and sent to a biasing circuit 133 as
well as the tone decoder 135.
[0112] FIGS. 10A-10B provide a detailed timing diagram showing how
the sync tone is used to synchronize the receiver 118 with the
transmitted signal. When the sync tone is transmitted, the tone
decoder 135 detects the tone after a (predictable) delay time of
TD. The value of TD includes the time for the signal to propagate
down the metal channel 128 as well as trigger the amplifying and
biasing circuit 133 and/or the tone decoder 135, such as the LM567.
Once triggered, the tone decoder 135 pulls down a general purpose
I/O (GPIO) on the DSP 122, such as the F2407A. The GPIO wakes up
the DSP 122 from its power-efficient mode and activates the
necessary peripherals to start receiving and processing the
received ultrasonic signal. The DSP 122 waits for a specified time
of T/2-TD+TM, where TM represents a safety margin to ensure the DSP
122 takes samples near the center of the received signal pulse. The
DSP 122 may sample at a rate of 165 KHz for a total sampling time
of TS, and may collect 512 samples. The time interval in which
sampling occurs is depicted by the shaded region in FIG. 10B. Once
512 samples are collected, a radix-2 FFT is performed on the
samples. The magnitude of the FFT is then compared to a threshold
at specific frequency bins corresponding to the frequency tones of
the MFSK modulation.
[0113] FIGS. 11 and 12 show the FFT results of two example MFSK
symbols. Shown in FIG. 11 is the actual real-time output of the DSP
122, as taken from a screen capture of the memory contents. Shown
in FIG. 12 is the actual real-time output of the DSP 122, as taken
from a screen capture of the memory contents. Annotations f0 to f15
have been super-imposed on the graph. The hexadecimal
representations of these symbols are 0xAAAA and 0x5555. Thus, these
are examples of MFSK symbols 116 for N=16 and Q=8. Although some
extraneous frequencies are present (e.g., between f13 and f14 on
both figures) they do not impact detection of the MFSK symbol 116,
because detection is performed by thresholding only the frequency
bins associated with the N=16 MFSK tones.
[0114] Referring now to FIG. 13, shown therein is a block diagram
of an exemplary module 130. More specifically, FIG. 13 is a block
diagram of an exemplary module 130 adapted to be positioned on an
interior surface 156 of an enclosure 154 (FIG. 15). The module 130
depicted in FIG. 13 includes a first transceiver 132, a second
transceiver 134, one or more controllers 136, and a power supply
138. The first transceiver 132 can be a wired or a wireless
transceiver 132 and is used for communication with communication
devices other than another module to typically collect data
indicative of conditions or devices on the interior of the
enclosure. Examples of communication devices include environmental
sensors(s), actuator(s), RFID tags and the like. The second
transceiver 134 can comprise an ultrasonic transceiver 100a
typically including a piezoelectric element (although other types
of elements can be used) for communicating with another module
using the metal channel 128 (e.g., a corner post 104a-b) as
discussed above.
[0115] The controller 136 can be formed of a collection of digital
and analog electronics including but not limited to: DSP (digital
signal processor); FPGA (field programmable gate array); ASIC
(application specific integrated circuit); memory/storage; DAC
(digital to analog converter); ADC (analog to digital converter);
and analog circuitry such as amplifiers, waveform shaping,
rectifiers, filters and the like. The controller 136 can be
programmed with computer executable instructions that when executed
by a processor, such as DSP 122 causes the controller 136 to enable
the first transceiver 132 and the second transceiver 134 to
communicate as discussed above. In particular, the computer
executable instructions can be in the form of a variety of
different types of functional logic, such as FFT (fast Fourier
transform); spectral decomposition; signal generation; encoding
scheme(s); decoding scheme(s); filtering; data compression
scheme(s); error detection/correction scheme(s); automatic gain
control; integration among multiple transceivers based on multiple
modes of communication (e.g., ultrasound, RF, IR, wired); human
interaction (e.g., through keypad for input from human and display
for output to human); interaction among multiple communication
protocols (e.g., 802.11, TCP/IP, custom ultrasonic, and GPS); and
communication schemes for highly fading and multipath channels
(e.g., ultrasound through steel) including MFSK and/or FSK.
[0116] The power supply 138 can be implemented in a variety of
manners such as non-rechargeable battery(s); rechargeable
battery(s); and motion/vibration/thermal energy harvesting.
[0117] Referring now to FIG. 14, a block diagram of an exemplary
embodiment of a module 140 adapted to be positioned on an exterior
surface 158 of an enclosure 154 (FIG. 15) is shown. The module 140
depicted in FIG. 14 includes a first transceiver 142, a second
transceiver 144, one or more controllers 146, a power supply 148 an
input unit 147 and an output unit 149. The second transceiver 144
can be a wired or a wireless transceiver 144 and is used for
communication with communication devices other than another module
to typically communicate data collected from the module 130
depicted in FIG. 13 to the other communication device. Examples of
communication devices include other modules, portable readers,
wireless networking equipment and the like. The first transceiver
142 can comprise an ultrasonic transducer 100b typically including
a piezoelectric element (although other types of elements can be
used) for communicating with another module using the metal channel
128 (e.g., a corner post 104a-b) as discussed above.
[0118] The controller 146 can be formed of a collection of digital
and analog electronics including but not limited to: DSP (digital
signal processor); FPGA (field programmable gate array); ASIC
(application specific integrated circuit); memory/storage; DAC
(digital to analog converter); ADC (analog to digital converter);
and analog circuitry such as amplifiers, waveform shaping,
rectifiers, filters and the like. The controller 146 can be
programmed with computer executable instructions that when executed
by a processor causes the controller 146 to enable the first
transceiver 142 and the second transceiver 144 to communicate as
discussed above. In particular, the computer executable
instructions can be in the form of a variety of different types of
functional logic, such as FFT (fast Fourier transform); spectral
decomposition; signal generation; encoding scheme(s); decoding
scheme(s); filtering; data compression scheme(s); error
detection/correction scheme(s); automatic gain control; integration
among multiple transceivers based on multiple modes of
communication (e.g., ultrasound, RF, IR, wired); human interaction
(e.g., through keypad for input from human and display for output
to human); interaction among multiple communication protocols
(e.g., 802.11, TCP/IP, custom ultrasonic, and GPS); and
communication schemes for highly fading and multipath channels
(e.g., ultrasound through steel) including MFSK and/or FSK.
[0119] The power supply 148 can be implemented in a variety of
manners such as non-rechargeable battery(s); rechargeable
battery(s); motion/vibration/thermal energy harvesting and a solar
power supply for harvesting solar energy.
[0120] The input unit 147 can be a keypad, touch screen or the
like; and the output unit 149 can be a display, printer, or the
like.
[0121] Referring now to FIG. 15, shown therein are a first module
140 and a second module 150, positioned on an enclosure 154 with
module 140 positioned on an interior surface 156 of the enclosure
154 and module 150 positioned on an exterior surface 158 of the
enclosure 154.
[0122] Referring now to FIG. 16, shown therein are a first module
140 and a second module 150 positioned on the enclosure 154 with
module 140 positioned on a bottom interior surface 160 of the
enclosure 154 and module 150 positioned on an exterior surface 158
of a sidewall 159 of the enclosure 154.
[0123] Referring now to FIGS. 17A and 17B, shown therein is an
enclosure 154 formed by a shipping container 162. The shipping
container 162 is shown as having four corner posts 104a-d. The
shipping container 162 has one or more internal surfaces 156 and
one or more external surfaces 158.
[0124] Referring now to FIG. 18A shown therein is a stack 164 of
shipping containers 162. The stack 164 is shown as having three
shipping containers 162, with corner posts 104 abutting one
another. Referring now to FIG. 18B, shown therein are two corner
posts 104 of two shipping containers 162 from the stack 164, with
the corner posts 104 abutting one another, and a floor 166 of a
first shipping container 162 disposed above a ceiling 168 of a
second shipping container 162.
[0125] Referring now to FIG. 19, shown therein is an exemplary
embodiment of non-axial single shipping container communication
system 170 according to the instant disclosure having modules 140
and 150 positioned on an interior surface 156 and an exterior
surface 158 respectively, of one of two shipping containers 162
forming a stack 164, and with modules 140 and 150 spaced apart
axially from one another.
[0126] Referring now to FIG. 20, shown therein is an embodiment of
the stack 164 comprising two stacked shipping containers 162
showing an example of axial single shipping container communication
system 172 having modules 140 and 150 positioned on the interior
surface 156 and the exterior surface 158 respectively of one of the
shipping containers 162 and with the modules 140 and 150 being
aligned axially with one another.
[0127] Referring now to FIG. 21, an exemplary embodiment of a
communication system 174 shown therein comprises: (1) ultrasonic
communication through abutted corner posts 104 between two modules
140a and 140b positioned on interior surfaces 156a and 156b of
adjacent shipping containers 162, (2) wireless communication
between a portable reader 176 held by an individual 178 and a
module 150 positioned on an exterior surface 158 of a shipping
container 162, and (3) wired or wireless communication between a
module 140b positioned on an interior surface 156b of a shipping
container 162 and sensor(s)/actuator(s) 180 or RFID tag(s) 182
positioned within the interior of the shipping container 162. The
modules 140 and 150 may also support other types of communication
modalities between one another inside of the shipping container
162; which include, infrared (IR), etc.
[0128] Referring now to FIG. 22, the communication system shown
therein has (1) ultrasonic communication through abutted corner
posts 104 between three modules 140a-c positioned on interior
surfaces 156 of adjacent shipping containers 162, (2) wireless
communication between a portable reader 176 held by an individual
178 and a module 150 positioned on an exterior surface 158 of a
shipping container 162, (3) wired or wireless communication between
modules 140a-c positioned on an interior surface 156 of a shipping
container 162 and sensor(s)/actuator(s) 180 or RFID tag(s) 182
positioned within the interior of the shipping container 162, (4)
at least one module 150a positioned on an exterior surface 158 of a
shipping container 162 having one or more wireless transceivers for
communicating with a GPS network 186, and one or more networks 188
to pass data to a computer 190 using a LAN and/or an Internet. In
general, the modules 140 and 150 can be a source, destination, or
relay points with relation to a network 188.
[0129] Referring now to FIG. 23, shown therein is a stack 164 of
shipping containers 162 having a generic distribution of modules
140 and 150 on abutting shipping containers 162 with each shipping
container 162 having zero or more modules 140 and 150, and modules
150 being on interior surfaces 156 and modules 150 being on
exterior surfaces 158 of the shipping containers 162.
[0130] Referring now to FIG. 24, shown therein is a matrix 192 of
M.times.L.times.N shipping containers 162. The shape of the matrix
192 may be generally, but not necessarily, square or rectangular.
Each shipping container 162 may have zero or more communication
modules 140 and 150 (not shown). Adjacent structures may or may not
be abutted/touching/connected. In summary, two or three dimensional
configuration of structures may exist (e.g., shipping containers
162).
[0131] Referring now to FIG. 25, the signal of interest is assumed
to be represented as a spectral line. By sampling at a specific
frequency, the signal's spectral line will fold (i.e., intentional
alias) to a lower frequency in the spectrum. This concept allows
the convenient determination if a signal is on or off by sampling
at a low frequency.
[0132] Shown in FIG. 26 is a block diagram of an exemplary module
140 adapted to be connected to the interior surface 156 of the
enclosure 154. The module 140 has a housing 194 defining an
interior space 196, and a sleeve 198 defining a bore 200. An
ultrasonic transducer 100 is positioned within the bore 200 of the
sleeve 198 and is urged out of the bore 200 by a biasing device
202, such as a spring. A first transceiver 204, power supply 206,
and controller 210 are preferably positioned within the interior
space 196 of the housing 194. The module 140 is also provided with
one or more attachment devices 212 which are shown by way of
example as magnets for coupling the module 140 to a metal
structure. The magnets 212 offer several advantages, such as
non-intrusive installation not requiring bolts, welding, or glue
while being relatively easy to install, maintain, and/or remove.
However, it should be understood that the module 140 could be
designed to use intrusive coupling mechanisms, such as bolts,
welding or glue(s). In the example shown in FIG. 26, magnets enable
the module 140 to be instantly mounted/dismounted onto a metal
surface without compromising/modifying the surface. When mounted,
the face of the transducer 100 can be held in compression on the
surface by the force provided by the biasing device 202, such as a
compressed spring.
[0133] The housing 194 is preferably constructed of a rugged,
non-corrosive material such as plastic that may also be pervious to
RF.
[0134] The magnet-based mounting system of the module depicted in
FIG. 26 enables modules to be mounted/dismounted quickly from a
surface and without compromising the surface. A module may be
mounted/dismounted on the outside of numerous distinct shipping
containers by a single operator within a short time span to query
information from modules mounted on the inside of various distinct
shipping containers that are either directly or indirectly in
contact with the shipping container on which the operator mounts
the external module. The description of a magnet-based quick
mount/dismount module does not preclude the use and installation of
more permanently mounted modules via bolts, epoxies, or welding.
The power supply (which may include batteries) of modules that are
used in this manner by an operator may be re-charged and/or
replaced periodically.
[0135] The instant disclosure describes the design of an MFSK
communication system based on ultrasonic signals transmitted
through steel shipping container corner posts via conformally
mounted low cost transducers. We have demonstrated the ability to
reliably encode and transmit a word of data that is encoded as an
MFSK symbol. Experiments conducted show that inexpensive
transducers are capable of both transmitting and receiving
ultrasonic signals through steel with a relatively high
signal-to-noise ratio and low transmit power. An exemplary
embodiment of a system according to the instant disclosure uses
inexpensive parts to build a working receiver with a data rate of
about 800 bps. Low-power aspects are further enhanced by leveraging
software defined radio techniques to implement a bandpass sampling
strategy (i.e., undersampling). Currently, our data transmission is
limited by how quickly the low-cost F2407A can perform an FFT. With
an upgraded DSP chip, the potential to be able to receive data more
quickly will be limited only by the intersymbol interference (ISI)
of the channel. Future developments may include specific MFSK
symbol encodings as well as communication protocols. A complete
transmitter/receiver module may also be implemented that is capable
of sensing and storing data from an array of sensors.
[0136] From the above description, it is clear that the inventive
concept(s) disclosed herein is well adapted to carry out the
objects and to attain the advantages mentioned herein as well as
those inherent in the inventive concept(s) disclosed herein. While
presently preferred embodiments of the inventive concept(s)
disclosed herein have been described for purposes of this
disclosure, it will be understood that numerous changes may be made
which will readily suggest themselves to those skilled in the art
and which are accomplished within the spirit of the inventive
concept(s) disclosed and claimed herein.
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